Affordable Access

Access to the full text

Valleyite: A new magnetic mineral with the sodalite-type structure

Authors
  • Lee, Seungyeol
  • Xu, Huifang
  • Xu, Hongwu
  • Jacobs, Ryan
  • Morgan, Dane
Type
Published Article
Journal
American Mineralogist
Publisher
Mineralogical Society of America
Publication Date
Aug 28, 2019
Volume
104
Issue
9
Pages
1238–1245
Identifiers
DOI: 10.2138/am-2019-6856
Source
De Gruyter
Keywords
License
Yellow

Abstract

Valleyite, Ca4(Fe,Al)6O13, is a new sodalite-type mineral discovered in late Pleistocene basaltic scoria from the Menan Volcanic Complex near Rexburg, Idaho, U.S.A. It is an oxidation product of basaltic glass during the early stage of the scoria formation and is associated with hematite (α-Fe2O3), maghemite (γ-Fe2O3), luogufengite (ε-Fe2O3), and quartz on the surface of vesicles. The measured crystal size of valleyite ranges from ~250 to ~500 nm. The empirical chemical formula of valleyite is (Ca3.61Mg0.39)(Fe3.97Al1.91Ti0.09)O13. The mineral has a space group of I4̅3m. The (Fe,Al)-O bond distance and unit-cell edge are slightly larger than those reported for synthetic Ca4Al6O13, presumably due to the presence of the larger Fe3+ cations, compared with Al3+, in the structure. Density functional theory calculations predict that valleyite may be a metastable phase at low temperatures. Measured Curie temperatures for valleyite and luogufengite are 645 and 519 K, respectively. Their magnetization hysteresis loop indicates the magnetic exchange coupling between valleyite (soft magnet) and luogufengite (hard magnet) that aids in the understanding of magnetic properties and paleo-magnetism of basaltic rocks. This new mineral, valleyite, with the sodalite-type cage structure is potentially a functional magnetic material.

Report this publication

Statistics

Seen <100 times